The Minimum-power Effect of a Magnetized Plasma

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   Abstract. An experimental and theoretical analysis is performed of a fully ionized, magnetized, quasi-steady plasma being separated from a surrounding neutral gas blanket by partially ionized boundary regions: (i) For rotating as well as high-frequency heated plasmas there exists a sharply defined minimum heating power P[m] and temperature T[0m] below which a steady fully ionized state cannot be maintained. At laboratory dimensions and ion densities of about 10^21 m^-3, these parameters become P[m] simeq 0.5 MW and T[0m] simeq 2 × 10^4 K. This "minimum-P effect" is important both to the processes of creating and maintaining laboratory plasmas in fusion research and to the studies of certain cosmical plasmas. (ii) The theoretically predicted behaviour of the plasma is roughly in agreement with the experiments in the power range close to the minimum value.